One of door trims for use with a vehicle is disclosed in Japanese Unexamined Patent Application Publication No. 2007-83899. In the art, the door trim has an armrest that protrudes from a wall of the door trim toward an inside of a compartment of the vehicle. The armrest is integrally formed with the door trim. The armrest has a grooved thin portion in an inner surface thereof. In the event of side impact to the vehicle, the armrest is pushed against a person located in the compartment. The armrest is then deformed along the thin portion and in a direction from an outer surface thereof toward the inside of the vehicle compartment. As the result of this deformation, impact to the person located in the vehicle compartment is reduced.
There are various materials that are used to form the door trims. For example, there is a case where resin foam molding is used to form the door trim. However, where molding resin foam is used to form the armrest having the grooved thin portion, the resin foam tends to shrink more easily in the grooved thin portion than in the portions around the grooved thin portion. Because of this shrink, sink marks are easily generated in the armrest. Therefore, in order to prevent generation of the sink marks, it is considered to form the entire armrest thinly and without forming the grooved thin portion.